Previous influenza pandemics have resulted in 50-100 million deaths worldwide, while seasonal influenza viruses cause between 3000 and 50,000 deaths and 200,000 hospitalizations per year in the US alone. The recent emergence of highly pathogenic avian H5N1 and H7N9 strains and the 2009 H1N1 influenza pandemic emphasize the continuing threat to human health and national security posed by pandemic influenza. To address this threat, annual universal vaccination is recommended for all individuals aged over 6 months in the US. Current vaccines include inactivated trivalent split or subunit and live attenuated vaccine, both of which have the drawback that they must be grown using laborious methods in eggs and reformulated every year based on the influenza strains predicted to be prevalent in the next flu season. However, the major disadvantage of these vaccines is a surprising lack of effectiveness, which was highlighted in a recent meta analysis of influenza vaccine (live and inactivated) in the US. Even in the recent 2012-13 season in which the vaccine was well-matched to circulating strains, only 59% efficacy was achieved, casting doubt on the long- standing belief that a close match between the vaccine and circulating strains results in high effectiveness. There is an urgent need for the development of highly effective and cross-protective influenza vaccines and new rapid methods of manufacturing. To meet this need FluGen has developed a novel vaccine virus (M2SR) based on the deletion of the M2 gene. This deletion in the viral genome allows for single replication of the vaccine virus in the host an production of viral proteins, which induces strong cross-protective immunity without the generation of progeny virions (shedding), a goal unmet by current vaccine strategies. The M2SR is a platform backbone virus that can be modified to encode the viral antigens from any influenza strain and is produced in a novel cell culture system, avoiding the use of eggs. We hypothesize that M2SR will provide safe, highly effective, broad spectrum, long-lasting protection against influenza. Our preliminary data support this hypothesis and show that the vaccine elicits strong systemic and mucosal immune responses and provides effective cross-reactive protection against lethal challenge with influenza. We will test this hypothesis in 4 Specific Aims: Aim 1. To determine the efficacy and spectrum of protection afforded by the M2SR vaccine. We will further investigate the efficacy and longevity of protection against homologous and heterologous viral challenge. Aim 2. To evaluate the safety profile of the vaccine. Lung histology and the inflammatory response will be assessed after vaccination and challenge. We will also conduct a toxicology study and determine the effect of pre-existing influenza infection on the vaccine. Aim 3. To determine the mechanism of heterologous protection. We will investigate the role of virus-specific T and B cell responses in cross-protection. Aim 4. To determine how the vaccine impact susceptibility to secondary bacterial infection. These studies will provide a comprehensive pre-clinical evaluation of the efficacy and safety of the M2SR vaccine.